The present invention relates to a process and apparatus for the removal of soot and condensable particles from the exhaust gases of a diesel engine.
Disclosed in U.S. Pat. No. 4,593,748 is a process for cleansing of hot exhaust gases from an engine, particularly a diesel engine, wherein the hot exhaust gases are cooled on surfaces of a heat exchanger cooled by a heat transfer medium. This causes the precipitation on surfaces of the heat exchanger of soot particles and volatile, condensable matter within the hot exhaust gases. This achieves a partial cleansing of the exhaust gases. Eventually, the precipitated soot and condensable matter accumulates on the surfaces of the heat exchanger, and when the heat exchanger surfaces largely or completely become saturated, such precipitate must be removed, i.e. the heat exchanger must be regenerated. This is done essentially by a self-heating and self-ignition process. However, complete removal of the precipitated soot and condensable matter is difficult by this procedure.
British GB-PS 293,431 discloses a further process for the removal of soot and volatile, condensable matter from diesel engine exhaust gases. In this process, the hot diesel engine exhaust gases are cooled on cold or cooled surfaces in a heat exchanger, thereby achieving partial cleansing with partial precipitation of soot and volatile, condensable matter. Additional cleansing and precipitation of residual soot and volatile, condensable matter occurs on additional precipitation surfaces, particularly in an electrostatic precipitation device. This procedure however discloses nothing regarding regeneration of the heat exchanger.
European EP 0 346 803 discloses an arrangement for the continuous removal of soot and volatile, condensable matter from diesel engine exhaust gases, wherein the hot exhaust gases alternately are conveyed through two heat exchangers, with a heat transfer medium acting on a secondary side of each heat exchanger and cooling the exhaust gases on a primary side of each heat exchanger. In this process, when one heat exchanger becomes partially or completely saturated with soot particles and condensed matter, the heat transfer medium supply to such heat exchanger is stopped. As a result, the hot exhaust gases heat the heat exchanger and the soot particles and condensed matter such that they burn off. The hot exhaust gases then are passed through another heat exchanger wherein partial cleansing of the hot exhaust gases occurs, with resultant precipitation of soot and condensable matter. The cooled exhaust gases containing residual soot and condensed matter then are conveyed through, for example, electrostatic precipitation devices. The operation of the plural heat exchangers is alternate between partial cleansing and regeneration.